Powertrain control architectures include systems for monitoring operation of various components and subsystems to ensure proper control and operation of the system based thereon, and to identify component and system faults. This includes devices and control algorithms which monitor ambient conditions. Vehicle manufacturers typically use an engine key-on test to detect a fault in an ambient pressure sensor by comparing its reading against another monitored pressure in the vehicle, e.g., turbocharger boost pressure and oil pressure. A similar method is used to detect faults in ambient air temperature sensors, typically after a soak period, wherein output of the ambient air temperature sensor is compared to an engine coolant temperature sensor or other sensor.
On-board fault detection and diagnosis of ambient pressure and air temperature sensors for automotive application can be challenging, since these sensor readings are affected by ambient conditions but typically not affected by other on-vehicle conditions. In other industries where accurate sensor readings affect ongoing system performance, e.g., the aerospace industry, multiple redundant sensors of the same critical type are deployed. Such systems utilize a voting technique whereby readings among the sensors are compared and used to detect a sensor fault, permitting the remaining sensor signals to be used to provide fault-tolerant control and monitoring. In the automotive industry, however, use of redundant sensors is typically cost-prohibitive.
Emissions-related diagnostics regulations typically require evaluation and detection of a fault in any sensor which affects emissions. A sensor fault can comprise an out-of-range fault, which is defined as an open circuit, i.e., zero volts output, or a short circuit, i.e., an output fixed at the power-supply voltage. A sensor fault can comprise an in-range fault, which is typically defined as a fault occurring in a sensing system wherein signal output of the sensing system is not a ‘true’ reading of the sensed parameter and not an out-of-range signal. An in-range sensor fault can be caused, for example, by sensor contamination or corrosion in a sensor wiring harness which skews the output signal.
Currently, automotive OEMs detect only open/short circuit faults in ambient air temperature and pressure sensors. There has been no effective in-range fault detection for systems which monitor ambient conditions beyond those occurring at vehicle start-up. However, the ambient pressure and temperature sensor readings can be used in engine control, e.g., to correct boost and adjust EGR flow. At high altitude, due to the ambient pressure drop, an ambient pressure or temperature sensor in-range failure can cause a turbocharger to over-speed, which can result in excessive heat and damage thereto. Therefore, prompt detection of in-range sensor faults can protect engine hardware and facilitate meeting future emissions regulations.
There is a need for an improved method to monitor and evaluate in-range performance of ambient sensors to address the issues described. Such a method is described hereinafter.